1. Field of the Invention
The invention relates to the field of saw mills. More particularly, the invention relates to shingle saw mills.
2. Description of the Prior Art
Definitions and usage: Shingles and shakes are relatively thin tapered slices of wood, typically cut from cedar logs. Each shingle has a butt, a top, two sides, and two planar faces. The thicker end of the tapered slice is the butt and the thin end the top. The side profile of the shingle is that of an isosceles triangle, with the two planar faces slanting from the butt to the top. The terms “shingle” and “shake” are often used interchangeably in the industry, and the term “shingle” shall be used hereinafter to encompass both the shingle and the shake.
The shingle industry has existed in the US for over 200 years. Producing a shingle from a log is a multi-step process, beginning with cutting a length of log that is slightly longer than the length of the finished shingle product, cutting a tapered rough blank or billet from a log, then squaring it up to a shingle by cutting a square butt edge and parallel side edges that are squared to the butt edge. A grading operation is performed manually, in which shingles are given a quality grade. There is no universal industry standard for this grading, so, for purposes of illustration only, an arbitrary grading system that defines quality grades #1 to #3 will be used in this specification. It should be understood, however, that the grading system may change according to order, with #1 identifying the highest quality grade and #3 the lowest acceptable grade. Thus, quality grade #3 may be different for an order that demands the highest quality from that of the standard order. Shingles that do not qualify as #3 are either discarded as waste or possibly cut for shims. The goal of this scanning operation is to maximize certain desirable characteristics or properties, such as size and/or quality, eliminate defective material, and reduce unnecessary waste.
As presently done, the sawyer receives a rough blank from the rough-billet saw, which may have live edges, that is, the round of the tree, still on the billet. The sawyer holds the shingle manually over an edging saw, with the butt placed against a flat support, and trims or edges first one side edge so that it is substantially perpendicular to the plane of the butt, flips the shingle, and trims the second side edge so that it is substantially parallel to the first side edge. These edges may not be perfectly square relative to the butt, so the shingles are typically sent through a re-squaring and re-butting machine, which “squares up” the shingle billet, that is, trims the sides so that they are perpendicular to the plane of the butt.
The conventional milling process results in significant and unnecessary removal of material from the width of the shingle, which reduces the amount of product or value that can be obtained from each log and increases the amount of waste product.
What is needed therefore is an automated process of grading, edging, rebutting, and sorting shingles. What is further needed is such a system that provides a safer work environment by reducing the exposure of the sawyer to saw blades. What is yet further needed is such a system that processes shingles faster and with much less waste production, and maximizes the amount of product that can be recovered from a log.